Intro To Endocrine Flashcards
Regarding chronotropic control of hormones, which is true?
- Negative feedback mechanisms inhibit chronograph frequency
- Results in an efficient response to stimuli in real time
- The pituitary receives neural stimuli to set a rhythm
- Continuous hormone frequency typically results in greater receptor sensitivity
- Results in an efficient response to stimuli in real time
How can cytokines and neurotransmitters fit the definition of hormone?
A hormone is a chemical messenger produced by a synthesizing cell and acting on a target cell which is exactly what cytokines and neurotransmitters do
Insulin is a hormone produced by the pancreas. Describe the region of the pancreas that produces insulin and how it supports the definition of a hormone synthesizing gland.
A hormone synthesizing gland is ductless. Insulin is produced by the islets of langerhans which are ductless regions of the pancreas but the pancreas also has acinus/ductal cells that are associated with digestive enzymes. The pancreas is therefore both an exocrine and endocrine gland
Describe why thyroxine is an amine derived hormone while thyrotropin releasing hormone
is a protein hormone.
Thyroxine (fat soluble) is derived from the addition of iodine to tyrosine (an amino acid) and then the condensation of 2 tyrosines that were harvested from a protein.
thyrotropin releasing hormone (water soluble) is a protein that is translated in the RER, modified in the golgi and packaged in secretory vesicles.
Insulin, hypothalamic hormones, anterior pituitary hormones are all examples of what hormone class?
Protein derived
Sex hormones, adrenal hormones are examples of what hormone class?
Steroid derived
How are protein derived hormones produced?
mRNA-ribosome- preprohormone- prohormone-active hormone Translation followed by proteolytic cleavage and chemical modification
How are steroid hormones produced?
Chemical modification of cholesterol side chains
How are amine derived proteins produced?
Chemical modification of amino acids
Tyrosine can be modified by hydroxylations into what water soluble hormones?
Catecholamines (dopamine, epinephrine, norepinephrine)
Tyrosine can be modified by condensation (loss of OH group) of two molecules into what lipid soluble hormones?
Thyroxine (thyroid hormones)
Tryptophan can be chemically modified to form what hormones?
Melatonin and serotonin
Glutamic acid can be chemically modified to form what hormone?
Histamine
What is the solubility of peptide/protein derived hormones?
Water soluble
What is the solubility of steroid derived hormones?
Lipid soluble
What is the solubility of amine derived hormones?
Water or lipid, depending on chemical modification
How are protein derived hormones stored?
In vesicles in the blood, ECF, synthesizing cell or target cell
How are steroid derived hormones stored?
In the ECF bound to albumin or other specific transport protein/globulin, however storage is limited, therefore they are made on demand
Thyroid hormone, catecholamine, melatonin, histamine are examples of what class of proteins?
Amine derived
In what form are protein derived hormones stored?
Typically in their active form, however they can be proteolytically cleaved after release into the ECF to their active form.
Example: angiotensinogen is stored in vesicles and released to ECF where it is cleaved by renin into angiotensin 1 and further cleaved by ACE into angiotensin 2
What is the rate limiting step of synthesizing steroid hormones?
Transport of cholesterol from the cytosol to the mitochondrial matrix for modification
What is the solubility of stercosteroid derived hormones?
Lipid soluble
What is the solubility of eicosanoids?
Lipid soluble
How are secosteroids produced?
Breaking a ring and other modifications of cholesterol
Where are secosteroids stored?
Skin, liver, kidneys
What is a classic examples of a secosteroid?
Vitamin D
What creates oxysterols (associated with pathology) from cholesterol?
ROS
How are ecosanoids produced?
Modification of arachadonic acid of a phospholipid
How are eicosanoids stored?
They are not. Instead they are made on demand